Method for automatically configuring network addresses in mobile multi-hop network

ABSTRACT

The present invention relates to a method for automatically configuring network addresses of mobile nodes participating in a mobile multi-hop network. The method of the present invention includes a first step of, if a first mobile node belonging to a first network moves into and participates in a second network, detecting that the first mobile node has moved; a second step of securing a route from the first mobile node to a gateway of the second network and requesting network configuration information; and a third step of receiving an available network address allocated by the gateway and changing the network configuration information of the first mobile node.

This application claims the priority of Korean Patent Application No.10-2003-0057685 filed on Aug. 20, 2003, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Apparatuses and methods consistent with the present invention relate toconfiguring addresses of mobile nodes present in a mobile network, andmore particularly, to automatically configuring network addresses ofmobile nodes participating in a mobile multi-hop network.

2. Description of the Related Art

A mobile ad hoc network provides a service to enable multi-hop basedcommunications by connecting mobile terminals to one another by means ofwireless links. Systems employing conventional wireless LAN basednetworks are constructed by connecting wired links to wireless links viaaccess points. In such systems, since the coverage of the wireless linksis not beyond the coverage within which the wireless links are directlyconnected to the access points, the access points can directlycommunicate with and control all terminal nodes. That is, mobile nodescan find access points and gain access to the Internet throughconnection with the found access points. In addition, a problem relatingto allocation of an address system suitable to a current network, andthe like can be overcome through direct communications among respectivenodes.

However, in a mobile ad hoc network in which connection to access pointsis made using multi-hops to overcome limitations on the coverage ofconventional networks, the access points cannot communicate directlywith all terminal nodes. Under these circumstances, in order that eachterminal node finds an access point and is allocated a network addressfrom the access point for efficient access to the Internet, there is aneed for a new mechanism that does not assume direct communication withaccess points.

In other words, when an access point for connection with the Internet isconnected to an ad hoc based network, a mobile node has to be able todetect its own movement and find the access point, which relays theconnection with the Internet, with a minimum network overload. Inaddition, the process of allocating the mobile node a network address bythe access point and connecting the mobile node with the Internet usingthe allocated network address should be automatically and efficientlyperformed.

A conventional technique for performing such a process is shown inFIG. 1. In a conventional Bluetooth or wireless LAN based network, anaccess point (AP) 110 is connected to mobile nodes 111, 112 and 113,which are managed by the access point 110, within one hop. In order thatthe mobile nodes 111, 112 and 113 connected to the access point 100 viawireless links may be connected with the Internet 100, they utilize theaccess point 100 connected with the Internet using a wired or wirelesslink.

In such a configuration of a conventional network, all mobile terminalnodes can communicate directly with an access point. As for conventionaltechniques relating to such a configuration, International PublicationNos. WO 00/176154, WO 01/37497 and WO 02/23342 disclose unicast routingfor an ad hoc network itself.

In the conventional technique shown in FIG. 1, since all the mobileterminal nodes 111, 112 and 113 can communicate directly with the accesspoint 110, the access point can easily detect a mobile node 120 newlyconnected to the access point 110. If the new mobile node 120 isdetected, this means that the mobile node 120 has moved. Then, theaccess point 110 confirms, based on a MAC address, whether the mobilenode 120 belongs to a network under current management, and the accesspoint 110 then relays connection of the mobile node 120 with theInternet 100. At this time, due to differences between address systems,there may occur a case where a new IP address should be configured forthe mobile node 120. In this case, a user manually configures a new IPaddress in a network using a static IP, whereas the mobile node 120 isallocated a new IP address via a dynamic host configuration protocol(DHCP) in a network using a dynamic IP.

In the conventional technique, as shown in FIG. 1, it is assumed thatthe mobile terminal nodes 111, 112 and 113 and the access point 110 areconnected directly to each other within one hop of the access point anda newly moved mobile terminal node also enters within one hop of theaccess point. In this case, the moved node can easily detect that thereis a change in an access point responsible for its connection with theInternet. Further, since the moved node is located at the distance ofone hop from a new access point, it is not necessary to find a routereaching the new access point for connection with the Internet.Moreover, as for the confirmation of an IP address, the user canmanually allocate an IP address to the moved node, or the moved node canbe easily allocated a new IP address using DHCP.

As described above, since the access point is connected, within only onehop, to all the mobile nodes managed by the access point in theconventional wireless LAN based network, the mobile nodes canefficiently find an access point for connection with the Internet andthen be easily connected to the access point. In addition, problemsrelating to the allocation of an address system suitable for a currentnetwork, and the like can be easily solved.

However, in a mobile ad hoc network environment where mobile nodes areconnected to one another through mobile multi-hops, only some of themobile nodes can communicate directly with an access point within onehop and there are many cases where a new mobile node that has enteredthe network is not within one hop of the access point. Accordingly, whena mobile node has moved, it is difficult to detect that the connectionof the mobile node to the access point for connection with the Internethas been changed. Further, there is a problem in that a route reaching anew access point should be found.

In addition, during the process of confirming an IP address, a mobilenode that cannot communicate directly with an access point shouldreceive an acknowledgement message through multi-hops of the ad hocscheme. Accordingly, since the mobile node cannot use its own IP addressuntil the use of the IP address is acknowledged by the access point,there is a problem in that it is difficult for the mobile node totransmit a message to the access point and receive a message from theaccess point.

As described above, in the mobile add hoc environment where mobileterminal nodes are connected to one another through mobile multi-hops,an access point cannot communicate directly with all the mobile terminalnodes. Therefore, when a mobile node moves, the whole processes by whichthe moved mobile node finds a route to an access point for connectionwith the Internet, confirms an address suitable for an address system ofthe access point and the mobile node is actually connected with theInternet through multi-hops.

Under the conditions where there is no topology information on a routeand a destination, communications through multi-hops causes an increasein the number of broadcasts, resulting in the reduction in the overallefficiency of a network.

SUMMARY OF THE INVENTION

The present invention is conceived to solve the aforementioned problems.An aspect of the present invention is to provide a method for enabling amobile multi-hop based mobile node to detect its own movement.

Another aspect of the present invention is to provide a method forenabling a mobile multi-hop based mobile node to find an access pointwith minimum network overload so that the mobile node can be efficientlyconnected with the Internet.

A further aspect of the present invention is to provide a method forautomatically and efficiently configuring the processes of enabling amobile multi-hop based mobile node to be subjected to confirmation of anetwork address by an access point and to be actually connected with theInternet using the network address.

According to one aspect of the present invention for achieving theaspects, there is provided a method for automatically configuring anetwork address of a first mobile node newly participating in a mobilemulti-hop network, comprising a first step of, if the first mobile nodebelonging to a first network moves into and participates in a secondnetwork, detecting that the first mobile node has moved; a second stepof securing a route from the first mobile node to a gateway of thesecond network and requesting network configuration information; and athird step of receiving an available network address allocated by thegateway and changing the network configuration information of the firstmobile node.

According to another aspect of the present invention, there is provideda first mobile node newly participating in a mobile multi-hop networkand receiving an allocated network address, comprising a first means fordetecting that the first mobile node has moved, when the first mobilenode belonging to a first network moves into and participates in asecond network; a second means for securing a route from the firstmobile node to a gateway of the second network and requesting networkconfiguration information; and a third means for receiving an availablenetwork address allocated by the gateway and changing the networkconfiguration information of the first mobile node.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will become apparent from the following description ofexemplary embodiments given in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view showing a case where a mobile node moves into a networkusing an access point in the related art;

FIG. 2 is a view showing an example where a mobile node moves into andparticipates in a new network;

FIG. 3 is a view showing an example where a mobile network comprisingmobile nodes moves into and participates in a new network;

FIG. 4A is a view showing the structure of a Neighbor table;

FIG. 4B is a view showing the structure of a Gateway_Solicit_Cachetable;

FIG. 4C is a view showing the structure of a Gateway Advertisement Type1packet;

FIG. 4D is a view showing the structure of a Gateway Advertisement Type2packet;

FIG. 4E is a view showing the structure of a Gateway Advertisement Type3packet;

FIG. 4F is a view showing the structure of a Gateway Solicit Type1packet;

FIG. 4G is a view showing the structure of a Gateway Solicit Type2packet;

FIG. 5A is a view showing the transmission and reception of hellomessages among neighbor nodes;

FIG. 5B is a view showing the contents of a Neighbor table of node 1that are updated through the hello messages in FIG. 5A;

FIG. 5C is a view showing the contents of a Neighbor table of node 3that are updated through the hello messages in FIG. 5A;

FIG. 5D is a view showing the contents of a Neighbor table of node 5that are updated through the hello messages in FIG. 5A;

FIG. 6 is a view showing the process of transferring a GatewayAdvertisement Type1 packet;

FIG. 7A is a view showing the process of transferring a Gateway SolicitType1 packet;

FIG. 7B is a view showing the contents of a Gateway_Solicit_Cache tablepossessed by nodes 3 and 5 in FIG. 7A;

FIG. 7C is a view showing the contents of a Gateway_Solicit_Cache tablepossessed by node 1 in FIG. 7A;

FIG. 8 is a view showing the process of transferring a Gateway SolicitType2 packet to a gateway;

FIG. 9 is a view showing the process of transferring a GatewayAdvertisement Type2 packet;

FIG. 10 is a view showing the process of transferring a GatewayAdvertisement Type3 packet; and

FIG. 11 is a flowchart illustrating entire processes for the operationof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

As shown in FIG. 2, in a mobile network environment, mobile nodes canrandomly move to withdraw from an existing network or participate in anew network. Further, a new mobile node that does not belong to anynetworks can be generated and included in a specific network. As shownin FIG. 2, in any mobile networks, there exist nodes that can beconnected to an access point within one hop to communicate directly withthe access point and to gain access to the external Internet.Furthermore, there exist nodes that cannot communicate directly with theaccess point because the nodes are at a distance of two or more hopsfrom the access point, but can communicate indirectly with the accesspoint using nodes connected to the access point within one hop. In theembodiments to be described below, it is assumed that the access pointsimultaneously has the function of a gateway for connection with theexternal Internet.

That is, any network is considered a combination of an infrastructuresystem comprising nodes directly connected to an access point and an adhoc system in which nodes communicate with one another in one-to-onecorrespondence regardless of an access point. When nodes moving fromother networks into or newly added to a new network are not connecteddirectly to an access point, the nodes should find a route to the accesspoint serving as a gateway for access to the external Internet andsecure an address to be used in the new network.

In addition to a case where individual nodes move into and participatein a new network as shown in FIG. 2, there may occur a case where all ora part of an ad hoc based network moves into and participates in anexisting network as shown in FIG. 3. When two networks are combined witheach other in such a manner, newly participating nodes should beidentified and managed as new members of the existing network.Accordingly, since the nodes newly participating in the network arerequired to be distinguished from existing nodes in the network, networkIDs enabling identification of networks are allocated to respectivenodes in accordance with the present invention.

As shown in FIG. 3, node 1 201, node 3 203 and node 9 209 with a networkID of A move and are connected to node 3 303 and node 5 305 with anetwork ID of B. At this time, the nodes with the network ID of A shouldbe able to communicate with node 8 308, i.e., an access point, throughthe nodes with the network ID of B in order to connect with theInternet. To this end, node 1 201, node 3 203 and node 9 209 with thenetwork ID of A should find a route to node 8 308 with the network ID ofB, receive network addresses and information on network configurationrelated thereto that can be used in the network B, and configure theirown network information according to the received network addresses andinformation.

In such a process, there may occur a case where network addresses ofnodes present in different networks may conflict with one another andthus the nodes cannot be used during such a process. Therefore, in orderto send information to a node newly participating in the network,support of a neighbor node is required. That is, node 1 201 with thenetwork ID of A can transmit and receive messages to and from thenetwork B by means of support of node 3 303 or node 5 305 with thenetwork ID of B, and node 3 303 and node 5 305 with the network ID of Bcan transmit and receive messages to and from the network A by means ofsupport of node 1 201 with the network ID of A.

FIGS. 4A to 4G show the structures of cache information tables possessedby each node and the structures of message packets to betransmitted/received between nodes, according to the present invention.Each of the tables and packets commonly includes network ID informationproposed by the present invention.

First, FIG. 4A shows the structure of a Neighbor table 410 storinginformation on neighboring nodes of each node. Since nodes may be addedor deleted randomly in an ad hoc network environment, information on aNetwork Address field (NW addr) 411 and a Hardware Address field (Hwaddr) 412 of nodes in the Neighbor table is updated bytransmitting/receiving hello messages among the nodes at a predeterminedtime interval. Here, the network address means a protocol address suchas an IP address, and the hardware address means a unique identifier orphysical address of hardware such as a MAC address. Finally, theNeighbor table 400 comprises a Network ID field (NW ID) 413, whichinforms that each node is included in which network and enablesidentification of each network.

FIG. 4B shows the structure of a Gateway_Solicit_Cache table 420, whichis a table for storing information on a node that has transmittedGateway Solicit Type1. The table 420 comprises a Neighbor Address field421 in which a network address of the node that has transmitted GatewaySolicit Type1 is recorded, a MAC Address field 422 in which a MACaddress of the node is recorded, and a Network ID field 423 in which anetwork ID of the node is recorded.

FIG. 4C shows the structure of a Gateway Advertisement Type1 packet 430through which a sending node informs a receiving node of information ona gateway of a network to which the sending node belongs. The packet 430includes a field 431 indicating that the packet is a GatewayAdvertisement Type1 packet, a Hop Count field 432 indicating the numberof hops to the gateway, a Sender Network ID field 433 in which a networkID of the sending node is recorded, a New Network ID field 434 in whicha network ID of the receiving node is recorded, a Sender's IP field 435in which a network address, i.e., an IP address, of the sending node isrecorded, a Sender's MAC field 436 in which a hardware address, i.e.,MAC address, of the sending node is recorded, and an Other Network Infofield 437 in which information on a route to the gateway and othernetwork information is recorded.

FIG. 4D shows the structure of a Gateway Advertisement Type2 packet 440informing nodes present in the same network of an address allocated by agateway. The packet 440 comprises a field 441 indicating that the packetis a Gateway Advertisement Type2 packet, a Sender Network ID field 442in which a network ID of a sending node is recorded, a Confirm IP field443 in which an IP address confirmed or newly allocated by the gatewayis recorded, a Sender's IP field 444 in which an IP address of a nodethat has transmitted a Gateway Solicit Type1 packet to a network towhich the gateway belongs is recoded, and a New Network ID field 445 inwhich an ID of the network to which the gateway belongs is recorded.

FIG. 4E shows the structure of a Gateway Advertisement Type3 packet 450informing nodes present in different networks of an address allocated bya gateway. The packet 450 comprises all fields, except for only theSender's IP field 444, in the Gateway Advertisement Type2 packet 440.

FIG. 4F shows the structure of a Gateway Solicit Type1 packet 460requesting a node present in a different network to transmit networkconfiguration information. The packet 460 comprises a field 461indicating that the packet is a Gateway Solicit Type1 packet, a SenderNetwork ID field 462 in which a network ID of a sending node isrecorded, a Sender's IP field 463 in which an IP address of the sendingnode is recorded, a Sender's MAC field 464 in which a MAC address of thesending node is recorded, and a New Network ID field 465 in which an IDof a network to which a receiving node belongs is recorded.

FIG. 4G shows the structure of a Gateway Solicit Type2 packet 470requesting a node present in the same network to transmit networkconfiguration information. The packet 470 comprises all fields, exceptfor only the Sender's MAC field 464, in the Gateway Solicit Type1 packet460.

The Gateway Advertisement Type1 packet 430, the Gateway AdvertisementType3 packet 450 and the Gateway Solicit Type1 packet 460 aretransmitted only to nodes with network IDs different from that of thenode that transmits the packets. On the contrary, the GatewayAdvertisement Type2 packet 440 and the Gateway Solicit Type2 packet 470are transmitted only to nodes with the same network ID. In such a way,it is possible to prevent erroneous transmission of data to nodes withdifferent network IDs and the same network address.

The operation of the present invention is performed through processesshown in FIGS. 5A to 10. Hereinafter, it is assumed that the node numberof a node in question indicates the network address of the node. Forexample, it is assumed that a network address of node 1 is ‘1’ and anetwork address of node 3 is ‘3.’

When node 1 201, node 3 203 and node 9 209 with the network ID of A hasmoved as shown in FIG. 3, the movement of the nodes is accomplishedthrough the nodes of a network that have moved and neighbor nodes ofanother network adjacent thereto, i.e., through node 1 201 with thenetwork ID of A, and node 3 303 and node 5 305 with the network ID of B.

In the mobile ad hoc network environment, hello messages 510, 520 and530 are periodically transmitted and received among the nodes, as shownin FIG. 5A, in order to detect the presence of neighboring nodes. Atthis time, the network ID identified by an access point and used by eachnode is included in the hello information and then transmitted. As aresult of transmission and reception of the hello messages, each nodereflects the contents of the hello messages on and updates its ownNeighbor table.

FIG. 5B shows an updated Neighbor table of node 1 201, wherein two rowsincluding network addresses, hardware addresses and network IDs of node3 303 and node 5 305 with the network ID of B are added to existinginformation on neighbor nodes. In addition, FIG. 5C shows an updatedNeighbor table of node 3 303, wherein one row including a networkaddress, a hardware address and a network ID of node 1 201 with thenetwork ID of A is added to existing information on neighbor nodes.Further, FIG. 5D shows an updated Neighbor table of node 5 305, whereinthe same row as added in FIG. 5C is added to existing information onneighbor nodes.

When nodes with different network IDs are added to the Neighbor tablesin such a manner, it can be determined that nodes which have receivedthe hello messages have moved or nodes with different network IDs havemoved. In the present invention, it is determined that nodes withdifferent network IDs have moved. In other words, node 1 201 determinesthat node 3 303 and node 5 305 have moved and approached node 1, andnode 3 303 and node 5 305 determine that node 1 201 has moved andapproached node 3 and node 5.

As shown in FIG. 6, node 1 201, node 3 303 and node 5 305 transmit theirown information on an access point, i.e., a gateway, to nodes withdifferent network IDs through a Gateway Advertisement Type1 packet. Inother words, node 1 201 with the network ID of A transmits a GatewayAdvertisement Type1 packet 610 including information on the gateway ofthe network A to node 3 303 and node 5 305 with the network ID of B.Specifically, node 1 201 informs node 3 303 and node 5 305 that a hopcount (432 in FIG. 4C) to the gateway is ‘3,’ a network ID (433 in FIG.4C) of the sending node is ‘A,’ a new network ID (434 in FIG. 4C) is‘B,’ an IP address (435 in FIG. 4C) of the sending node is ‘1,’ and aMAC address (436 in FIG. 4C) of the sending node is ‘0×ff34a5c8941b.’

Similarly, node 3 303 informs node 1 201 that a hop count (432 in FIG.4C) to the gateway is ‘1,’ a network ID (433 in FIG. 4C) of the sendingnode is ‘B,’ a new network ID (434 in FIG. 4C) is ‘A,’ an IP address(435 in FIG. 4C) of the sending node is ‘3,’ and a MAC address (436 inFIG. 4C) of the sending node is ‘0×ff34a508941b.’

Further, node 5 305 informs node 1 201 that the hop count (432 in FIG.4C) to the gateway is ‘3,’ a network ID (433 in FIG. 4C) of the sendingnode is ‘B,’ the new network ID (434 in FIG. 4C) is ‘A,’ the IP address(435 in FIG. 4C) of the sending node is ‘5,’ and the MAC address (436 inFIG. 4C) of the sending node is ‘0×ff3508405941.’

At this time, the Gateway Advertisement Type1 packet is transmitted toonly nodes with different network IDs within only one hop. Each of thenodes that have received the Gateway Advertisement Type1 packet selectsa node with a minimum hop count (432 in FIG. 4C) by referring to hopinformation contained in the Gateway Advertisement Type1 packet andtransmits the Gateway Solicit Type1 packet (460 in FIG. 4F) to theselected node. That is, node 1 210 with the network ID of A transmits aGateway Solicit Type1 packet 710 including a network address to be usedby node 1, i.e., the Sender's IP field (463 in FIG. 4F), to only node 3303 closer to the gateway of the network B. Further, since node 3 303and node 5 305 with the network ID of B have received the GatewayAdvertisement Type1 packet from only node 1 201, they transmit theGateway Solicit Type1 packets 710 and 730 including network addresses tobe used by nodes 3 and 5, i.e., the Sender's IP fields (463 in FIG. 4F),to node 1 201, respectively. The Gateway Solicit Type1 packets are alsotransmitted to only nodes with different network IDs within only onehop.

Each of the nodes that have received the relevant Gateway Solicit Type1packet stores the packet in its own Gateway_Solicit_Cache table (420 inFIG. 4B). FIG. 7B shows information stored in a Gateway_Solicit_Cachetable of node 3 303, and FIG. 7C shows information stored in aGateway_Solicit_Cache table of node 1 201.

Then, as shown in FIG. 8, each of the nodes that have received therelevant Gateway Solicit Type1 packet configures the Gateway SolicitType2 packet (470 in FIG. 4G) using information stored in its ownGateway_Solicit_Cache table and transmits the packet to the gatewayusing its own routing information. The Gateway Solicit Type2 packets(470 in FIG. 4G) are transmitted to only nodes with the same network IDthrough multi-hops.

At this time, node 1 201 that has received the Gateway Solicit Type1packets (720 and 730 in FIG. 7A) transmitted by node 3 303 and node 5305 intends to transmit Gateway Solicit Type2 packets to its own gatewayusing its own routing information. Since the packets should pass throughnode 9 209 to be transmitted to the gateway using the routinginformation, node 1 201 transmits the Gateway Solicit Type2 packets 820and 830 for node 3 303 and node 5 305 to node 9 209. However, since thenetwork A has no gateway, node 1 201 cannot receive any response theretofrom node 9 209. Accordingly, the contents (see FIG. 7C) recorded in theGateway_Solicit_Cache table of node 1 201 that has not received anyresponse are deleted due to time-out. On the other hand, since there isa gateway in the network B, node 3 303 that has received the GatewaySolicit Type1 packet (710 in FIG. 7A) transmitted by node 1 201transmits a Gateway Solicit Type2 packet 810 to node 8 308 that is agateway of node 3 303.

As described above, when nodes present in different networks approacheach other, one party determines that the other party has approached theone party and performs the aforementioned processes. However, it iseventually determined that node 1 201 in which the contents recorded inthe Gateway_Solicit_Cache table of node 1 201 have been deleted hasapproached the network B.

The gateway 308 that has received the Gateway Solicit Type2 packet 810from node 3 303 confirms whether it can use an address to be used bynode 1 201, i.e., the address of ‘1’ in the Sender's IP field of theGateway Solicit Type1 packet (710 in FIG. 7A). If a conflict occurs dueto the presence of the same address in the network B, the gatewayallocates a different address that is not present in the network B. Inthis example, since there exists a node 301 with the same address in thenetwork B, the gateway allocates a new address of ‘10’ to node 301.

The gateway informs node 3 303 of the allocation of the new address of‘10’ by transmitting the Gateway Advertisement Type2 packet (440 in FIG.4D) thereto. This packet is finally transmitted to a neighbor node,i.e., node 3 303, with a network ID different from that of the nodesthat have moved, as shown FIG. 9.

Then, as shown in FIG. 10, node 3 303 transmits the GatewayAdvertisement Type3 packet (450 in FIG. 4E), including the availablenetwork address of ‘10’ allocated by the gateway 308, to node 1 201 byusing the information (see FIG. 7B) of the Gateway_Solicit_Cache tableof node 3 303. Node 1 201 that has received the Gateway AdvertisementType3 packet changes its own network information using the informationof the Gateway Advertisement Type1 packet (620 in FIG. 6) received inadvance and information of a Gateway Advertisement Type3 packet 1010,and secures a route to the gateway 308 of the network B. Consequently,node 1 201 changes its own network ID to ‘B’ and its own network addressto ‘10’ and finds the route to the gateway 308 by referring to thecontents of the Other Network Info field (437 in FIG. 4C) of the GatewayAdvertisement Type1 packet (620 in FIG. 6). Accordingly, node 1 201becomes a member of the network B. Next, node 1 201 serves as an arbiterof node 3 203 and node 9 209 with respect to the network B in the samemanner as node 3 303 which has performed the processes for node 1 201,so that node 3 203 and node 9 209 can also become members of the networkB through the same processes.

FIG. 11 is a flowchart illustrating entire processes for the operationof the present invention.

First, steps S101 to S103 correspond to the process of detectingmovement of new mobile nodes when the new mobile nodes move into andparticipate in a mobile multi-hop network.

Mobile nodes with a first network ID move and approach a second networkwith a second network ID (S101). That is, more than one of theapproaching nodes enter the second network to be within one hop frommore than one of nodes belonging to the second network. Next, hellomessages are transmitted and received among the nodes that belong to thedifferent respective networks and connected to one another through onehop (S102). Each hello message includes information on the network ID,network address and hardware address of the sending node. Accordingly,if it is confirmed that the network ID included in each hello message isdifferent from that of the network to which a node in question belongs,it is possible to detect that the sending node, which has transmittedthe hello message, has moved.

The nodes that have received the hello messages each of which includesthe network ID, the network address and the hardware address of thesending node add the contents of the hello messages to their ownNeighbor tables (S 103).

Second, steps S104 to S107 correspond to the process by which the mobilenodes that have moved into and participated in the second network secureroutes to a gateway and request network configuration information.

As in step S103, when information on a node with a different network IDis added to a Neighbor table of a node in question, the node that hasreceived the information determines that the sending node approaches thenetwork of the receiving node from the previous network of the sendingnode, and then transmits the Gateway Advertisement Type1 packet to thesending node (S 104).

The node that has received the Gateway Advertisement Type1 packettransmits the Gateway Solicit Type1 packet to the node that hastransmitted the Gateway Advertisement Type1 packet in order to requestnetwork configuration information (e.g., IP address and gateway routeinformation) of the network to which the node that has transmitted theGateway Advertisement Type1 packet belongs (S105). If there are aplurality of nodes that have transmitted Gateway Advertisement Type1packets, the Gateway Solicit Type1 packet is transmitted to only a nodewith a small hop count (432) in the Gateway Advertisement Type1 packet.

Then, the node that has received the Gateway Solicit Type1 packetupdates its own Gateway_Solicit_Cache table using the informationtransmitted through the Gateway Solicit Type1 packet (S 106).

Subsequently, the node that has received the Gateway Solicit Type1packet transmits the Gateway Solicit Type2 packet to the gateway usingits own routing information (S107). If the Gateway Solicit Type2 packethas to go through more than two hops to the gateway, it reaches thegateway via intermediate nodes.

Finally, steps following step S108 correspond to a process by which thenew mobile node that has moved into and participated in the new networkis allocated an available network address and changes its own networkconfiguration information.

The gateway that has received the Gateway Solicit Type2 packetdetermines whether an IP address recorded in the Sender's IP field ofthe Gateway Solicit Type2 packet is available in the network to whichthe gateway belongs (S108). If the same IP address is not present inaddress data of the gateway, the IP address recorded in the Sender's IPfield is allocated to the new mobile node (S109). If the same IP addressis present in the address data of the gateway, a new different IPaddress is allocated to the mobile node (S110).

A Gateway Advertisement Type2 packet including the allocated IP address(Confirm IP) is transmitted to the node that has previously received theGateway Solicit Type1 packet (S111). Even in this case, if the GatewayAdvertisement Type2 packet has to go through more than two hops from thegateway to the node that has previously received the Gateway SolicitType1 packet, the Gateway Advertisement Type2 packet reaches the nodevia intermediate nodes.

Thereafter, the node that has finally received the Gateway AdvertisementType2 packet transmits a Gateway Advertisement Type3 packet to the nodethat has transmitted the Gateway Solicit Type1 packet (S112). Then, thenode that has received the Gateway Advertisement Type3 packet becomes amember of the new network by changing its own network configurationinformation such as an IP address and a route to the gateway (S113).

However, there may be a case where even though a node transmits aGateway Solicit Type2 packet to a gateway of a network to which the nodebelongs as in step S107, it does not receive any response from thegateway. This case means that although the node has information on thegateway of the network to which the node was connected previously, thereis no gateway connected to the network to which the node belongs atpresent. Accordingly, this case can be considered as corresponding to acase where the network to which the node belongs has moved.

According to the present invention described above, it is possible toquickly perform a process by which multi-hop based mobile nodes detecttheir movement using their network IDs and secure information on anaccess point or gateway in a new network.

In addition, according to the present invention, it is also possible toreduce network overhead that is produced while multi-hop based mobilenodes obtain network addresses and network configuration information andare then connected with the Internet.

Furthermore, according to the present invention, it is possible toautomatically perform a process by which network addresses of multi-hopbased mobile nodes are confirmed by access points and the mobile nodesare actually connected with the Internet using the confirmed networkaddresses.

Although the present invention has been described in connection with theexemplary embodiments of the present invention, it can be understood bythose skilled in the art that various modifications and changes may bemade thereto without departing from the scope and spirit of theinvention. Therefore, it should be understood that the above embodimentsare not limitative, but merely illustrative in all aspects. The scope ofthe present invention is defined by the appended claims rather than thedetailed description. All modifications and changes derived from thescope and spirit of the claims and equivalents thereof should beconstrued as falling within the scope of the present invention.

1. A method for automatically configuring a network address of a first mobile node newly participating in a mobile multi-hop network, comprising: (a) if the first mobile node belonging to a first network moves into and participates in a second network, detecting that the first mobile node has moved; (b) securing a route from the first mobile node to a gateway of the second network and requesting network configuration information of the second network; and (c) receiving an available network address allocated by the gateway and changing network configuration information of the first mobile node.
 2. The method as claimed in claim 1, wherein (a) comprises: approaching, by the first mobile node, a second mobile node belonging to the second network by moving toward the second mobile node to be within one hop; transmitting and receiving hello messages between the first and second mobile nodes; and storing contents of the hello messages.
 3. The method as claimed in claim 2, wherein each of the hello messages includes a network ID, a network address and hardware information of a respective sending node.
 4. The method as claimed in claim 1, wherein (b) comprises: transmitting a first packet including information on the gateway of the second network to the first mobile node; transmitting a second packet requesting the network configuration information of the second network to the second node that has transmitted the first packet; and transmitting a third packet requesting network configuration information of the second network to the gateway, using information of the second packet and routing information.
 5. The method as claimed in claim 4, wherein, if there are more than two nodes transmitting respective first packets, the second packet is transmitted only to one of the more than two nodes with a small hop count to the gateway from information of the first packets.
 6. The method as claimed in claim 4, wherein the first packet includes: information on a hop count to the gateway; information on an ID of the second network to which the second node transmitting the first packet belongs; information on an ID of the first network to which the first mobile node receiving the first packet belongs; information on an IP address of the second node transmitting the first packet; and information on a MAC address of the second node transmitting the first packet.
 7. The method as claimed in claim 4, wherein the second packet includes: information on an ID of the first network to which the first mobile node transmitting the second packet belongs; information on an IP address of the first mobile node transmitting the second packet; information on a MAC address of the first mobile node transmitting the second packet; and information on an ID of the second network to which the second node receiving the second packet belongs.
 8. The method as claimed in claim 4, wherein the third packet includes: information on an ID of the first network to which the first mobile node transmitting the second packet belongs; information on an IP address of the first mobile node transmitting the second packet; and information on an ID of the second network to which the second node receiving the second packet belongs.
 9. The method as claimed in claim 1, wherein (c) comprises: determining, based on address data of the gateway, whether a network address used by the first mobile node is available; allocating the network address as an allocated network address if it is determined that the network address is available, or allocating a new available network address as the allocated network address if it is determined that the network address is not available; transmitting information on the allocated network address to the first mobile node; and changing the network configuration information of the first mobile node.
 10. The method as claimed in claim 9, wherein the operation of determining whether the network address is available is made based on whether the network address is used in the address data of the gateway.
 11. The method as claimed in claim 9, wherein the operation of transmitting the information on the allocated network address to the first mobile node comprises: transmitting a fourth packet including the information on the allocated network address to a second mobile node neighboring the first mobile node; and transmitting a fifth packet to the first mobile node, using the fourth packet.
 12. The method as claimed in claim 11, wherein the fourth packet includes: information on a network ID of the first network to which the first mobile node belongs; information on an IP address allocated by the gateway; information an IP address of the first mobile node; and information on a network ID of the second network to which the second mobile node belongs.
 13. The method as claimed in claim 11, wherein the fifth packet includes: information on a network ID of the first network to which the first mobile node belongs; information on an IP address allocated by the gateway; information on a network ID of the second network to which the second mobile node belongs.
 14. The method as claimed in claim 9, wherein the network configuration information of the first mobile node includes information on a route to the gateway and information on an IP address.
 15. A first mobile node newly participating in a mobile multi-hop network and receiving an allocated network address, comprising: a detector operable to detect that the first mobile node has moved, when the first mobile node belonging to a first network moves into and participates in a second network; a second means for securing a route from the first mobile node to a gateway of the second network and requesting network configuration information of the second network; and a third means for receiving an available network address allocated by the gateway and changing network configuration information of the first mobile node.
 16. The mobile node as claimed in claim 15, wherein the movement of the first mobile node is detected through transmission and reception of hello messages between the first mobile node and a second mobile node that belongs to the second network and is located within one hop from the first mobile node, each of the hello messages including a network ID, a network address and hardware information of a respective sending node.
 17. The mobile node as claimed in claim 15, wherein the request for the network configuration information is made by receiving a first packet including information on the gateway of the second network from a second mobile node, and transmitting a second packet requesting the network configuration information of the second network to the second mobile node that has transmitted the first packet.
 18. The mobile node as claimed in claim 17, wherein, if there are more than two nodes transmitting respective first packets, the second packet is transmitted only to one of the more than two nodes with a small hop count to the gateway from information of the first packets.
 19. The mobile node as claimed in claim 17, wherein the first packet includes: information on a hop count to the gateway; information on an ID of the second network to which the second node transmitting the first packet belongs; information on an ID of the first network to which the first mobile node receiving the first packet belongs; information on an IP address of the second node transmitting the first packet; and information on a MAC address of the second node transmitting the first packet.
 20. The mobile node as claimed in claim 17, wherein the second packet includes: information on an ID of the first network to which the first mobile node transmitting the second packet belongs; information on an IP address of the first mobile node transmitting the second packet; information on a MAC address of the first mobile node transmitting the second packet; and information on an ID of the second network to which the second node receiving the second packet belongs.
 21. The mobile node as claimed in claim 15, wherein the available network address is not used in address data of the gateway.
 22. The mobile node as claimed in claim 15, wherein the network configuration information of the first mobile node includes information on a route to the gateway and information on an IP address. 